Is data integration mostly a problem with top SaaS apps (e.g. Salesforce), or is it an issue with the "long tail" of apps used by most companies?

I do believe that the long tail is very important for data integration. Fivetran focuses on their 150-200 connectors, but if you look at their incentives, they obviously want to focus on the products with the biggest customers (with the biggest bank accounts) and the largest customer base.

That said, if you go talk to the Seed or Series A or Series B companies, it becomes pretty clear that their customers do want data warehouse integrations—whether they have customers that just set up their warehouse for the first time or whether they're trying to sell into those enterprise markets and trying to compete with the Salesforces or the other companies with the connectors already built in. 

Data warehouse integration is an extremely important problem and increasingly becoming something that companies are concerned about, and I think we'll continue to see companies investing in integration as a capability, whether it's via some sort of outsourced connector via Airbyte or Fivetran or by building the connector themselves.